8.4.1 Implementation Defined Options

THROW-codes used in the system:

The codes -256−-511 are used for reporting signals. The mapping
from OS signal numbers to throw codes is -256−signal. The
codes -512−-2047 are used for OS errors (for file and memory
allocation operations). The mapping from OS error numbers to throw codes
is -512−errno. One side effect of this mapping is that
undefined OS errors produce a message with a strange number; e.g.,
-1000 THROW results in Unknown error 488 on my system.